1. Field of the Invention
The present invention relates to a process for the continuous preparation of synthetic resin plates having an irregular flow pattern of different colors.
2. Description of the Related Art
A plate of different colors having a color pattern on the surface thereof is known, and plates of this type are prepared according to various processes. For example, there can be mentioned a process in which a plate is formed and a pattern is printed on the plate by using paints differing in color, and a process in which a film having a color pattern printed thereon is bonded to a plate. However, plates of different colors prepared according to these conventional processes have a poor durability and the colored surface film is liable to be separated from the surface of the plate by an external force or with the lapse of time. Moreover, when such a plate is subjected to heating or drawing, wrinkles are formed because of the difference in stretchability between the surface color film and the base plate, or the color becomes thin in the drawn portion and the color difference between the drawn portion and the undrawn portion becomes prominent, resulting in degradation of the aesthetic effect.
Processes for the preparation of plates of different colors are disclosed in U.S. Pat. Nos. 3,488,246, 3,529,325, 3,562,379, 3,570,056, and 3,706,825, and Japanese Unexamined Patent Publication No. 60-9714. According to the teachings of these U.S. patents, a polymerizable liquid material including a filler and a colorant and having a high viscosity is appropriately mixed with a colorant liquid having a low viscosity by using a three-staged mixing means, and the polymerizable liquid material is polymerized and cured to obtain an opaque plate-shaped product having a pattern resembling a marble pattern. The characteristic feature of this preparation process resides in that the polymerizable material is appropriately mixed. However, the pattern is changed according to the concentration, viscosity and flow rate, and the state of the mixer, and the probability of the formation of a predictable pattern on the surface of the plate is low. It is thus difficult to produce an aesthetic color pattern with a good reproducibility. ducibility. The technique disclosed in Japanese Unexamined Patent Publication No. 60-9714 is one developed by us. According to this technique, at least two polymerizable liquid materials differing in color are extruded from two groups of flow paths, the outlets of which are combined alternately, and are introduced into a polymerization apparatus where the materials are polymerized and cured to obtain a plate having a linear pattern. A plate of different colors obtained according to this technique has only a linear pattern or grain pattern, and the fashion and design characteristics of the plate are not attractive.